title: Roles of larval sea urchin spicule SM50 domains in organic matrix self-assembly and calcium carbonate mineralization.
abstract: The larval spicule matrix protein SM50 is the most abundant occluded matrix protein present in the mineralized larval sea urchin spicule. Recent evidence implicates SM50 in the stabilization of amorphous calcium carbonate (ACC). Here, we investigate the molecular interactions of SM50 and CaCO3 by investigating the function of three major domains of SM50 as small ubiquitin-like modifier (SUMO) fusion proteins - a C-type lectin domain (CTL), a glycine rich region (GRR) and a proline rich region (PRR). Under various mineralization conditions, we find that SUMO-CTL is monomeric and influences CaCO3 mineralization, SUMO-GRR aggregates into large protein superstructures and SUMO-PRR modifies the early CaCO3 mineralization stages as well as growth. The combination of these mineralization and self-assembly properties of the major domains synergistically enable the full-length SM50 to fulfill functions of constructing the organic spicule matrix as well as performing necessary mineralization activities such as Ca(2+) ion recruitment and organization to allow for proper growth and development of the mineralized larval sea urchin spicule.
authors.affiliation: Physical Chemistry, Department of Chemistry, University of Konstanz, Universitätsstraße 10, PO Box 714, D-78457 Konstanz, Germany.
authors.forename: Ashit
authors.initials: A
authors.lastname: Rao
authors.forename: Jong
authors.initials: J
authors.lastname: Seto
authors.forename: John K
authors.initials: JK
authors.lastname: Berg
authors.forename: Stefan G
authors.initials: SG
authors.lastname: Kreft
authors.forename: Martin
authors.initials: M
authors.lastname: Scheffner
authors.forename: Helmut
authors.initials: H
authors.lastname: Cölfen
mesh_terms: D060105:Animal Shells / Q000254:growth & development* / Q000378:metabolism; D000818:Animals; D002119:Calcium Carbonate / Q000737:chemistry / Q000378:metabolism*; D003598:Cytoskeletal Proteins / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000378:metabolism; D016326:Extracellular Matrix Proteins / Q000378:metabolism*; D007814:Larva; D046529:Microscopy, Electron, Transmission; D012617:Sea Urchins / Q000196:embryology / Q000254:growth & development; D025841:Small Ubiquitin-Related Modifier Proteins / Q000378:metabolism; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D003598:Cytoskeletal Proteins; D016326:Extracellular Matrix Proteins; C051691:SM50 protein, sea urchin; D025841:Small Ubiquitin-Related Modifier Proteins; D002119:Calcium Carbonate
keywords: Amorphous calcium carbonate; Biomineralization; C-type lectin; CTL; GRR; IDP; Intrinsic disorder; Matrix assembly; PRR; SM50; SM50 structural domains; SUMO; Spicule matrix proteins; gly-rich region; intrinsically disorder protein; pro-rich region; small ubiquitin-like modifier; spicule matrix protein 50